We are comparing transient and long-term effects of cortisol on enzymes in 2 major metabolic pathways in small intestine and liver of developing rats. Alterations in the quantitative distribution and the developmental appearance of these enzymes in response to other modifications in physiological milieus are also being determined. Enzymes that catalyze sequential reactions in a common pathway are expected to respond coordinately in any one tissue. Differential response to environmental changes of the same enzyme in intestine and liver may signal dissimilar isoenzymes. To distinguish among isoenzymes, some biochemical properties of ornithine carbamyltransferase are being investigated and the isoenzymes will be separated physically. The developmental pattern of the appearance of isoenzymes will be determined to discover if the intestinal or the hepatic represents of the common fetal form. Since not all enzymes in either intestine or liver are stimulated equally by nutritional or hormonal manipulation, such treatments results in imbalances of enzymic composition. The long-term effects on growth and differentiated functions of intestine and liver will be studied in rats with such enzymic imbalances to determine a) if the effects are advantageous or detrimental, b) if and up to what ages these imbalances may be reversed, and c) if intestine and liver have equal competence to reestablish the normal developmental sequence of enzyme formation once it has been disturbed. Studies of enzymes involved in the metabolism of folate compounds and in transformations of ornithine and arginine will be emphasized.